IT'S HARD TO GET a word in when you chat to David de Rothschild. The passionate 31-year-old Brit has just completed his latest adventure - sailing a boat made of 12,500 recycleable plastic bottles across the Pacific from San Francisco to Australia.

He's talking about his epic journey from the 20-metre-catamaran, the Plastiki, moored in Southport on the Gold Coast when I speak to him. There he was waiting for favourable winds to sail down to Sydney.

The hyperactive environmentalist takes off on tangents - spilling informative facts, figures and philosophies. "God, I don't shut up do I!" he says by satellite phone from the Plastiki. "I'm sorry about my ranting." But he loves talking about it: "Keep asking!" he says.

David admits he's consumed by his passion for the environment and has spent over a decade quenching his environmental curiosity. "This is my life," he says. "You have to be almost childlike in your curiosity because as adults we don't ask questions, we just accept it."

This explains his motto: "You are only young once, but you can stay immature indefinitely." His latest mission was sparked four years ago by a desire to draw attention to the huge amount of waste in the ocean, especially plastic, and how this impacts the health of humans.

The danger of plastic ocean pollution

"EVERY SYNTHETIC PIECE OF plastic, every bit of plastic that's ever been produced is somewhere on our planet," David says. "It's in our atmosphere through incineration, it's in our ocean or in landfill or potentially still being used ... in someone's house, someone's cupboard, someone's bottom drawer."

He pulls this one from his mental database of facts: 61 per cent of the plastic in the ocean is less than one millimetre thick; these particles attract off-shore toxins that end up being ingested by humans through the food we eat. "You are exposing yourself to high levels of toxicity through the transference of toxins in the plastic in our oceans," he says.

To get people talking, David, inspired by the tightly-packed seeds in a pomegranate, collected 12,500 used plastic bottles, lashed them to a hull made of recycled plastic and created an "unconventional vessel". The Plastiki, inspired by the 1947 Kon-Tiki expedition, is self-sufficient, has bicycle generators, the mast is made of an irrigation pipe and the on-board vegetable garden is watered with urine.

"I wanted to design something that was aesthetically pleasing and was iconic and that captured people's imaginations," he says. "The last thing I wanted to do was for people to go, `Holy crap, there's that crazy, junk thing floating around'."

The platstic ship departs

A CREW OF 12 departed on 20 March. Only three British members - de Rothschild, skipper Jo Royale and co-skipper David Thomson - have been onboard for the entire journey. They've made three stops en route to Australia, have been followed by a pod of dolphins, spotted pilot whales and witnessed a lunar eclipse in the Pacific. After 125 days at sea they will sail through the heads of Sydney Harbour today, marking the end of this epic mission.

Despite having lots to say, David, who goes through phases of vegetarianism, doesn't preach from a soapbox. "I don't know all the answers, I'm definitely not some green saint. I don't judge people by what they do. I'm real with it," he says. "Kermit the frog sums it up: `It's not easy being green'."

David, a descendant of England's Rothschild banking dynasty, grew up on his family's country estate in England, riding horses at an elite level, sourcing his milk from the estate's cows and collecting eggs from hens for breakfast. "You were one with the environment," he recalls. "I was always a kid who was far more comfortable outside than in...I was bouncing around, this hyperactive kid, trying to get in and out of the window and try and be outside as much as possible."

The message in a bottle

AS A TEENAGER, HE became fascinated with "what you eat and what you breathe" and did a degree in natural medicine, completing the practical element of his studies at a clinic in Sydney in 2004.

"Once you start to delve deeply into what you eat and what you breathe you realise that you cannot separate the health of us as human beings from the health of our planet. It's so intrinsically linked, it's so obvious," David says. "This has been my world since I was 19 years old, all my adult life."

The "massively passionate" man, who has been named among Britain's hottest bachelors, relishes the challenge of engaging people in environmental issues. He says adventure, art and creativity are the best vehicles to communicate the messages he's spruiking. "That makes it engaging and exciting and I think people then can connect to it in a much more real and open way."

It's this philosophy that underpins the adventurers impressive list of achievements - he's the youngest Briton to reach both poles, is one of a handful of people to traverse Antarctica and was part of a team that broke the world record for the fastest-ever crossing of the Greenland ice cap.

The fast-talking greenie already has "another big cool, cool adventure" up his sleeve. "I can't tell you just now, but it's going to be very exciting."